This article originally appeared in the Health and Medicine print issue, in stands January 2025. It has not been updated and some information may be out of date.
January and February face the worst bouts of inversion in the Salt Lake Valley. While this poor air quality impacts sensitive asthmatic groups, the health ramifications of inversion expand beyond respiratory complications.
Many studies have researched Salt Lake specifically, showing that due to the unique geographical landscape of the city, warm air settles on top of cold air, trapping it into the valley.
Several studies have drawn links between child development inhibition and air pollution. One of the main areas of study follows the effects of PM2.5 — particulate matter 2.5 micrometers or less in diameter — on pregnancy.
“Outdoor PM2.5 comes primarily from combustion of gasoline, oil, diesel fuel, coal or wood,” stated Cotter et al. in their 2023 work. “Effects of ambient fine particulates, nitrogen dioxide and ozone on maturation of functional brain networks across early adolescence.” The authors also explained that PM2.5’s danger stems from its small size as this diminutiveness allows particles to enter the bloodstream via inhalation and cause systemic inflammation to individual’s bodies.
The World Health Organization recognizes PM2.5 as a major global risk factor for heart disease, stroke, chronic obstructive pulmonary disease, asthma, cancer and other noncommunicable diseases. More specifically, researchers are increasingly focusing on the effects of air pollution on children as many hypothesize increased susceptibility to these diseases during critical developmental periods.
Neurology
One specific area of study includes air pollution’s effect on the brain. Cotter et al.’s aforementioned study longitudinally examined the neurodevelopmental delays linked to air pollution.
The researchers evaluated the effect of O3, NO2 and PM2.5 on a group of 9-10-year-old children and completed a follow-up data set when the children were 11-13. The final analyses included 9,497 children with between one and two valid data points.
The study found that PM2.5 correlated with greater inter-network and subcortical-to-network functional connectivity, while high O3 exposure corresponded with greater intra-network interactions within the two-year follow up period. NO2 differed in that the researchers linked high exposure with decreased inter-network and subcortical-to-network functional connectivity.
Additionally, the study found that PM2.5 correlated with the most substantial changes in functional connectivity between subcortical brain regions in late childhood and early adolescence; however, O3 and NO2 were still significant.
The subcortical structures such as the amygdala and hippocampus are instrumental in emotional processing, motor control and cognition. While the study refrained from claiming direct impacts of these findings, the authors state air pollution may have important implications in cognitive and emotional processes “with potential consequences related to the emergence of psychopathologies.”
The bottom line of the study asserts that air pollution is associated with brain developmental differences of the functional brain networks for children as they transition into adolescence.
Peterson et al.’s 2015 study “Effects of Prenatal Exposure to Air Pollutants (Polycyclic Aromatic Hydrocarbons) on the Development of Brain White Matter, Cognition, and Behavior in Later Childhood” supports the findings of Cotter et al.
This study examined the impact of polycyclic aromatic hydrocarbons (PAHs) — air pollutants that often compose PM2.5 — through a cross-sectional study with children ranging from fetuses to nine years old.
The sample of 40 youths found a “dose-response relationship between increased prenatal PAH exposure” and reductions of the white matter surface of the left hemisphere of the brain in later childhood.
“Reduced left hemisphere white matter was associated with slower information processing speed during intelligence testing and with more severe externalizing behavioral problems, including attention-deficit/hyperactivity disorder symptoms and conduct disorder problems,” wrote Peterson et al.
These findings suggest that prenatal PAH exposure contributes to slower processing speeds that provide a possible explanation for attention-deficit or hyperactivity disorders in youth.
Pregnancy Loss
In addition to neurological impacts, several researchers have looked at pregnancy loss and its correspondence with air pollution exposure.
The 2024 work of Wesselink et al. found a “moderate association” between miscarriages or spontaneous abortions (SAB) and PM2.5 concentrations in Canada. The studies conducted in the United States were less conclusive.
The study examined “multiple critical windows of exposure including both preconception and prenatal periods” to address if there are stages more critical than others regarding air pollution’s impact on miscarriage.
As the study found higher associations in Canada than the U.S., the researchers highlighted differences in the composition of PM2.5 between the countries as a possible explanation. Canadian PM2.5 is composed of “wildfires and residential biofuel combustion” whereas there are “larger contributions from road transportation and coal in the U.S. [PM2.5].”
The researchers noted that regardless of their less strong associations in the United States, “the extensive body of literature documenting an association between prenatal air pollution exposure and risk of other adverse birth outcomes and pregnancy complications … remains an important measure to safeguard maternal and fetal health.”
Another study conducted by Leiser et al. in 2019 researched the acute effects of air pollutants on SAB in Salt Lake specifically.
The study extracted a final sample of 1,398 miscarriages from the University of Utah Enterprise Data Warehouse and compared air pollution exposure before a miscarriage event to “a similar window of exposure on days not associated with [SAB].”
Their research found that specific elevation of NO2 in air pollution is associated with spontaneous pregnancy loss.
“Approximately 50% of early pregnancy spontaneous loss are attributed to nonchromosomal abnormalities (29) and maternal exposure to combustion particles is associated with oxidative damage to DNA and lipids (30), which could be detrimental to the growing fetuses,” wrote Leiser et al.
The study also claimed that “exposure to air pollution has also been shown to inhibit embryo implantation, which is a risk factor for spontaneous pregnancy loss.”
Leiser et al. noted that most available literature “has found an increased risk of spontaneous pregnancy loss and air pollutant exposure,” in line with Wesselink et al.’s discussion.
Both Wesselink et al. and Leiser et al. list oxidative stress as a probable explanation for the air pollution-SAB association. Oxidative stress occurs when there is an imbalance of free radicals and antioxidants in the body, leading to cell damage.
Leiser et al. also listed endocrine disruption of the pregnant person and systemic inflammation creating “abnormal placentation and growth abnormalities” as effects of air pollution. This reference to inflammation remains common within the literature as Cotter et al. similarly raised inflammation as a health concern.
Conception
Researchers have also looked into air pollution’s impact on conception. Ren et al. in 2019 found that increased PM2.5 exposure in the air during the “periconception period” to be “modestly associated” with risk of congenital anomalies.
Ren et al.’s research demonstrates that the highest PM2.5 susceptibility occurs one month before and after conception.
“Although the increased risk with PM2.5 exposure is modest,” noted the researchers, “the potential impact on a population basis is noteworthy because all pregnant women have some degree of exposure” in Salt Lake.
In addition to pregnancy, some scientists have delved into air pollution’s impact on sperm as well. Hammoud et al. in 2010 researched decreased sperm motility and Salt Lake City’s air pollution.
The study measured PM2.5 levels and sperm motility — the ability of sperm to traverse the female reproductive organs to reach and fertilize an egg — through 1,699 semen analyses and 877 inseminations. The samples were exclusive to men in Salt Lake County within a set five-year period.
“Both semen analysis and sperm parameters data obtained from men presenting for multiple inseminations over time showed that air pollution is associated with reduced sperm motility two to three months after exposure,” wrote Hammoud et al.
Ramifications
Utah has witnessed a decline in its historically high birth rate. In recent years, Salt Lake has also seen some of the poorest air quality in the world. As of Dec. 4, 2024, Salt Lake had the 24th worst U.S. air quality. Last summer, Salt Lake had the 14th worst global air quality in the aftermath of wildfires.
Beyond the studies conducted in the Salt Lake Valley, there is also anecdotal evidence of the effects of air pollution. The Chronicle spoke with PhD student Winona Wood to discuss the intersection of environmentalism and health.
“We have a wealth of environmental justice literature that proves that environmental harms in society are distributed unequally along the lines of social stratification,” said Wood. She noted how marginalized communities live closer to the lake on the west side, exposing them to more pollutants proximity-wise.
Wood described how Salt Lake faces pollution in the form of individual car emissions, industrial waste and the drying Great Salt Lake. Grineski et al.’s research published last June estimates that “social disparities in dust fine particulate matter (PM2.5) exposures [are] based on four policy-relevant water-level scenarios” where “PM2.5 exposures would increase as GSL levels drop.”
Wood said students can “be a part of finding the solutions” that address both the social and environmental components of air pollution in the Salt Lake Valley.
